Compatibility of HRD/DM780 with Digi Portserver TS4

This article documents some compatibility issues experienced with HRD870 using a Digi Porterver TS4.

(Raydo 2012) described an interesting solution to remote station operation, and in his solution he used a Digi Portserver. These can be obtained used on eBay at modest prices (~$100 posted), and look like a possible solution to a remote station without a full blown computer at the remote site.

Initial tests

Initial tests with the TS4 were encouraging. The drivers installed in Win7 properly, and the ports were accessible and worked with a few test applications.

HRD 5.4 was tested with a TS4 port connected to a TS2000 over an on-site IP network, and it worked apparently fine.

DM780 was tested with another TS4 port connected to a Winkeyer type keyer, and it failed to initialise every time, yet the same keyer worked fine on a local COM port and on a local USB/COM adapter.

So, an interesting case exists where HRD can use the remote port just fine, and DM780 (which one might expect uses the same development framework and algorithms) does not work.

Further testing

In an attempt to gather more information, a series of tests were performed on the remote port.

Loopback with a number of applications

The remote port was testing using two terminal emulators and several other applications with an external hardware loopback on the remote port. All applications behaved as expected except DM780 which showed no received data in its log.


WKDemo is an application to demonstrate the Winkeyer and is nominated as a reference application.

It opened the remote Winkeyer type keyer and operated it just fine.

A trace of the communications interface was taken and it is at WKDemo trace.


DM780 failed to initialise the remote Winkeyer type keyer.

DM780's log showed it had sent data but received nothing.

A trace of the communications interface was taken and it is at DM780 trace.

Another IP remote RS232 server

Another remote RS232 server was tested. The solution was based on a Raspberry Pi running sercd with USB/RS232 adapters, and com0com / hub4com drivers on the WIn7 workstation.

That configuration worked fine with HRD / TS2000 and DM780 / Winkeyer type keyer, suggesting that DM780 was tolerant of the network latency, small as it is on a local IP network.

This solution is not nearly as elegant on the Win7 side as the Digi Portserver unfortunately, otherwise it might provide a good solution.


DM780 5.4 does not work with Digi Portserver TS4 ports, whilst WKDemo does work.

It would appear that there is something in the way that DM780 opens the port that is an issue with the Portserver virtual port, but interesting to note that HRD opens the same ports successfully and works fine.

The problem was logged on the HRD support forums, but in six weeks has had not response, not even acknowledgement (unsupported software?). There is the makings of a finger poking exercise here as HRD blames Digi and Digi blames HRD. DM780 was the only package of 6 tested that had issues with the TS4, and HRD knows how to use the TS4 port properly.

Undoubtedly, the mark of good software is that it works with all available ports, and of good port emulation, that it works with all available software. The experience shows that one or both fail that test.



Version Date Description
1.01 16/11/2012 Initial.

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